A blood test for Alzheimer’s that costs a fraction of the cost of a brain scan or spinal tap may be almost as accurate, according to new research.
The test, known commercially as Precivity AD, was developed by researchers at Washington University School of Medicine in St. Louis. It uses mass spectrometry to identify levels of proteins Aβ42 and Aβ40 in the blood. The ratio of these proteins can be used to determine the likelihood of amyloid plaque buildup in the brain, a hallmark of Alzheimer’s disease.
A study published early this month in the journal Neurology compared the results from the blood test to two common methods for identifying Alzheimer’s: a PET brain scan and analysis of cerebrospinal fluid from a spinal tap. The research found that, when combined with pre-screening for genetic risk, the blood test was 88% accurate compared to the brain scan and 93% accurate when compared to the spinal tap.
The research involved 465 patients from the United States, Australia and Sweden. The test was able to identify signs of Alzheimer’s in both patients who had and had not yet experienced cognitive decline.
The blood test is also significantly less expensive than the other methods of diagnosis. According to a university press release, the Precivity AD test costs about $500, compared to $1,000 for a spinal tap and close to $5,000 for a PET scan. Neurologist Randall Bateman, MD, who developed the test and co-authored the study, said it can also cut down on the amount of time needed to diagnose Alzheimer’s.
“A blood test for Alzheimer’s provides a huge boost for Alzheimer’s research and diagnosis, drastically cutting the time and cost of identifying patients for clinical trials and spurring the development of new treatment options,” Bateman said in the release. “As new drugs become available, a blood test could determine who might benefit from treatment, including those at very early stages of the disease.”
Previcity AD has been commercially available since 2020 under the FDA’s Clinical Laboratory Improvement Amendments (CLIA). That CLIA certification has made it available to U.S. doctors, and a similar approval clears the test for use in Europe. However, it is not yet covered by Medicare, Medicaid or most insurance.
A result from the blood test is a number on a scale of one to 100, referred to as an Amyloid Probability Score. A low score (zero to 36), indicates a low probability of plaque buildup, while a high score (58 to 100) shows a high probability of buildup. According to Previcity AD, 10-15% of patients will see an intermediate score (37-57), which means more diagnostic work is needed.